The present invention relates generally to bale opening devices, and more particularly to a method for controlling a bale opening device in order to extract or remove fiber flocks from a line or row of bales.
Bales of fiber material are normally laid down in rows on the spinning mill floor to form a xe2x80x9cbale laydown.xe2x80x9d The bale laydown may include a different number of bale groups. The height profile or surface contour of the bale laydown depends on a number of factors. For example, compression of the fiber material in the bales before the bale ties are opened, the relative humidity of the various bales, and the selection process applied by the mill operators for selecting and arranging the bales to be laid down in a given bale group are all factors affecting the profile or contour of the bale line.
Once the bales are arranged in the bale laydown, flocks are extracted by a computer controlled take-off element which covers generally the width of the bales in the bale line and which can be moved longitudinally along the upper surface of the bales. For this purpose, the contour or profile of the bales is usually scanned by corresponding sensors and the profile entered into a computer. Furthermore, based on a predetermined bale extraction program, a certain number of passes and the take-off depth per passage of the take-off element can be preset for a fiber layer height and the flocks can be extracted accordingly by the take-off element.
It is known in the art to control the take-off element program according to a number of factors. For example, it is known to use suitable height level sensors to scan the height profile of the bale line with the results being entered into a control device for controlling the take-off element as a function of density or hardness within the bale. U.S. Pat. No. 4,660,257 describes such a device wherein the extracting member or take-off element extracts fiber flocks from the upper bale surfaces with a penetration depth into the bales that is variably dependent on the bale height. The penetration depth of the extraction member is gradually reduced in an upper bale region doing a predetermined number of passes from a maximum value to a lesser penetration depth that has been determined for a middle bale region. The bales are subdivided into a plurality of height zones that exhibit different densities of fiber material. The penetration depth of the take-off element in a middle zone is maintained until reaching a lowermost zone in which the penetration depth is again gradually increased. The control system includes a microprocessor which stores inputted desired number of passes and penetration depths for the different height zones and controls the take-off element accordingly. This type of program control based upon a height density profile also has application in the present invention and will be described in greater detail herein.
U.S. Pat. No. 5,564,165 deals with a method of controlling the take-off element in order to reach an equalization of the different fiber bale heights so that the take-off element extracts the same depth of fiber material consistently along the bale line. According to the control method of the ""165 patent, the bale height of all the bales in the bale line is determined by sensors carried on the bale opener and input into a computer. The operator inputs into the computer a vertical feed or penetration depth of the detaching device for the bales in the bale line that have a minimum bale height. The operator also inputs a common bale height for all of the bales wherein no change in the penetration depth is required. It is at this height that equalization of the bales will have taken place. The computer then determines a proportionately higher feed for the bales other than those having the minimum bale height so that equalization is achieved at the common bale height. Thus, according to this control system, the spinning mill operator determines at which height equalizing of the bales heights is to be completed and the take-off depth for the lowest bale. The computer then calculates the take-off requirements needed for the higher bales to achieve equalization at the desired common height.
U.S. Pat. No. 5,105,507 describes another method for controlling a take-off element in a fiber extraction device wherein the height profile of the row of bales is determined by at least one sensor that is directed towards the upper bale surface. This sensor is preferably an optical or acoustical sensor and the received signal from the sensor is processed to obtain a signal corresponding to the hardness of the bales. The penetration depth of the take-off element is controlled or regulated in accordance with the hardness signal.
The present invention relates to a control method for a fiber extraction device that reliably and accurately accounts for bale height differences and density characteristics of the bale line.
It is thus a principal object of the present invention to provide an improved control method of operating a bale opening machine having a fiber extraction or take-off element for removing desired layers of fiber material from a row of bales.
Additional objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In accordance with the invention, a control method is provided for operating any manner of bale opening machine having a fiber extraction or take-off element controlled by a computer control system. It should be appreciated that the present control method is not limited to any particular configuration of bale opening machine, and has application wherever it is desired to control the penetration depth of the fiber extraction member or take-off element. The only requirement is that the bale opening machine have appropriate sensors for determining the bale heights or bale profile as described herein, as well as a control system for operating the take element. Although not essential to the invention, the bale opener is preferably provided with sensors enabling it to derive the necessary information. For example, bales may be laid down on opposite sides of a track along which the bale opener moves and the bale opener can process bales on one side of the track while a movable sensor, e.g. on a separate carriage, detects the heights or the profile of bales on the other side of the track.
In this regard, a method according to the invention is provided for operating a bale opening machine having a take-off device for removing a desired depth of material in a take-off layer from a top surface of a line of bales as the take-off device passes over the bale line. The method includes the step of determining a total height difference between a low point and a high point along the bale line. The high point may correspond to the highest or tallest of the bales and the low point may correspond to the lowest or shortest of the bales. This step of determining the total height difference may be carried out in any manner. For example, the height of the bales may be measured and the height difference calculated from the measured heights. In another embodiment, the total height difference may be determined based solely on a height differential of the bale profile. In other words, it is not critical that the actual heights of the bales relative to the mill floor be determined for this purpose. The concern is not the actual bale heights, but the difference in bale height between the highest and lowest points.
The method includes the step of defining a desired normal or operational take-off depth for the take-off device as a function of the necessary through put production of the bale opening machine. The through put production is related to a number of factors, including the downstream requirements in the fiber processing line.
Actual take-off depths for the take-off device are computed by the control system for predetermined control positions along the bales to be processed. The control positions may have a predetermined spacing and the control system configured so that the locations of the control positions are stored for use in each pass of the take-off element. The control positions may correspond to the individual positions at which the bale opener samples the bale line in an initial pass of the take-off element. The actual take-off depths are a function of the normal take-off depth and relative bale height at the respective positions along the bale line with respect to the total height difference. The take-off device is then controlled according to the actual take-off depths at the predetermined positions for each pass of the take-off device along the bale line.
Prior to each pass of the take-off device, a new total height difference is calculated or determined between the low and high points of the bale line. If the new total height difference is less than or equal to the magnitude of the normal take-off depth, then the control system sets the actual take-off depths for all points along the bale line to eliminate the effect of bale height equalizing factors applied to the value of the normal take-off depth.
The step of computing the actual take-off depths preferably comprises the step of assigning a minimum and maximum take-off factor for the low and high points of the bale line. Each such factor may be selected from a predetermined range stored in the control system. In a basic embodiment, this program range may not be variable. The factors may be selected independently from the program ranges. For example, respective ranges may be stored for the minimum take-off factor and the maximum take-off factor and a selection may be required from each range to compute take-off depths. Alternatively, the factors may be effectively xe2x80x9cpairedxe2x80x9d so that a selection of one of the two factors determines the other. The selection may be made in terms of a percentage of the available range. The factors may be preprogrammed in the system and xe2x80x9cretrievedxe2x80x9d based upon a measured or inputted bale height difference. For example, the operator may input an initial bale height difference and, based on this difference, the system will automatically select the appropriate range of the factors (provided variable ranges are programmed). Corresponding take-off factors for the control points along the bale line are then computed by the system as a proportional function of the ratio of the bale height difference at the respective positions to the total bale height difference. The computed take-off factors are then applied to the normal take-off depth to calculate the actual take-off depth at the respective control positions along the bale line. In other words, a maximum take-off factor is assigned to the highest bale height position and a minimum take-off factor is assigned to the lowest bale height position. Proportional take-off factors are computed for the other positions along the bale line based on the ratio of the height difference at the respective positions compared to the total height difference between the minimum and maximum bale heights.
In a preferred embodiment of the present control method, the initial set of take-off factors is applied for each subsequent pass of the take-off device until the total height difference between the high and low bale heights is reduced to at least the magnitude of the normal take-off depth. In this regard, the total height difference between the low and high points of the bale line is measured or computed prior to each pass of the take-off element. However, the take-off factors are not necessarily recomputed and the initial set of take-off factors may be used for each pass of the take-off element. The new total height difference may be computed prior to each pass based on the previous total height difference and the take-off depths at the high and low bale heights utilized in the previous pass of the take-off device. Thus, it should be understood that the new calculations may be carried out by the control system without relying on actual sensor inputs or signals relating to the bale heights.
The present method also preferably comprises steps for controlling the take-off depth at the positions along the bale line as a function of bale density by applying a bale density factor in the computation process for the actual take-off depths at the respective control positions along the bale line. The bale density factors may be based upon a predetermined or perceived bale density characteristic of the bales. The bale density factors may also be applied at discrete height portions of the bales. These discrete height portions may be defined as a percentage of initial bale height. For example, an operator may enter the perceived bale density characteristic into the control system of the bale opening device. The control system may have density factors stored therein corresponding to different bale density characteristics. The control system will apply the appropriate density factors to portions of the bales that are determined as a function of bale height. It may be preferred to apply the density factors to only a top and bottom portion of the bales. A middle height portion of the bales need not be corrected for density. The percentages that define the top and bottom portions may also be a factor of perceived bale density and also stored in the control system such that the operator need only to input the density characteristic of the bale. The control system will then apply the appropriate density factor and compute the appropriate height portions in which to apply the density factors.
The height take-off factors and density factors are then applied to the normal take-off depth to define the actual take-off depth at the control positions along the bale line. The take-off element is controlled as a function of the height take-off factors and density take-off factors for each pass of the take-off device.
FIG. 1 is a diagrammatic side elevational view of a conventional bale opening machine equipped with a type of control system which may be used to practice the present method;
FIGS. 2a-2c are operational diagrammatic views of the take-off element and sensor arrangement of a bale opening machine that may be used to practice the present method;
FIG. 3a is a diagrammatic view of a bale laydown illustrating certain principles of the present invention;
FIG. 3b is a diagram of a height profile for the bale laydown of FIG. 3a; and
FIG. 4 is a density compensation diagram illustrating certain principles of the present invention.